U.S. patent application number 14/754976 was filed with the patent office on 2016-01-07 for control apparatus and control method for controlling forming apparatus which forms concavo-convex structure.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Hideki Kadoi, Hideki Kubo.
Application Number | 20160001549 14/754976 |
Document ID | / |
Family ID | 53510568 |
Filed Date | 2016-01-07 |
United States Patent
Application |
20160001549 |
Kind Code |
A1 |
Kubo; Hideki ; et
al. |
January 7, 2016 |
CONTROL APPARATUS AND CONTROL METHOD FOR CONTROLLING FORMING
APPARATUS WHICH FORMS CONCAVO-CONVEX STRUCTURE
Abstract
A control apparatus configured to control a forming apparatus
which forms concavo-convex structure by ejecting ink obtains
concavo-convex data indicating the concavo-convex to be formed and
divide the concavo-convex data into a plurality of pieces of data.
The control apparatus controls a formation order, performed by the
forming apparatus, of the concavo-convex portions each
corresponding to the plurality of pieces of data divided by the
dividing unit based on a feature amount of the concavo-convex
indicated by the concavo-convex data.
Inventors: |
Kubo; Hideki; (Kawasaki-shi,
JP) ; Kadoi; Hideki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
53510568 |
Appl. No.: |
14/754976 |
Filed: |
June 30, 2015 |
Current U.S.
Class: |
347/9 |
Current CPC
Class: |
B33Y 10/00 20141201;
B41J 2/01 20130101; B41J 2/04586 20130101; B41J 2/2117 20130101;
B33Y 30/00 20141201; B29C 64/112 20170801; B41J 2/04536 20130101;
G05B 2219/49023 20130101; B33Y 50/02 20141201 |
International
Class: |
B41J 2/045 20060101
B41J002/045 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2014 |
JP |
2014-137905 |
Claims
1. A control apparatus configured to control a forming apparatus
which forms concavo-convex structure by ejecting ink, comprising:
an obtaining unit configured to obtain concavo-convex data
indicating the concavo-convex structure to be formed; a dividing
unit configured to divide the concavo-convex data into a plurality
of pieces of data for a plurality of scanning; and a control unit
configured to control the forming apparatus based on the plurality
of pieces of data, wherein the control unit controls a formation
order, performed by the forming apparatus, of the concavo-convex
portions each corresponding to the plurality of pieces of data
divided by the dividing unit based on a feature amount of the
concavo-convex indicated by the concavo-convex data.
2. The control apparatus according to claim 1, wherein the control
unit uses a degree of sharpness of the concavo-convex data as the
feature amount.
3. The control apparatus according to claim 1, wherein the dividing
unit generates pieces of slice data corresponding respectively to a
plurality of layers by dividing the concavo-convex data indicating
the concavo-convex to be formed, and the control unit controls the
forming apparatus in such a way that: a piece of the slice data for
an uppermost layer in a region of a sharp portion of the
concavo-convex is recorded in a last scanning operation for the
region; and other pieces of the slice data in the region of the
sharp portion are recorded in a reverse scanning order such that
apiece of the slice data for a lower layer is recorded in a
scanning operation in an earlier stage.
4. The control apparatus according to claim 3, wherein the control
unit controls the forming apparatus in such a way that the forming
apparatus sequentially records the pieces of slice data in a region
other than the region of the sharp portion of the concavo-convex,
from a piece of the slice data for a lower layer.
5. The control apparatus according to claim 1, wherein the forming
apparatus forms the concavo-convex by ejecting curable ink.
6. The control apparatus according to claim 1, wherein the
obtaining unit obtains data indicating a height of the
concavo-convex to be formed in each of pixels as the concavo-convex
data.
7. The control apparatus according to claim 1, wherein, in the
control unit, an operation condition for the forming apparatus in a
region having a predetermined feature amount is different from that
in a region having a feature amount other than the predetermined
feature amount.
8. The control apparatus according to claim 1, wherein the control
unit uses a frequency component of the concavo-convex data as the
feature amount.
9. The control apparatus according to claim 1, wherein the control
unit uses a degree of importance of height accuracy or inclination
angle accuracy as the feature amount.
10. The control apparatus according to claim 1, wherein the control
unit uses a feature amount of an image to be formed on the
concavo-convex formed by the forming apparatus as the feature
amount.
11. The control apparatus according to claim 1, wherein the
concavo-convex data is data indicating a height of the
concavo-convex to be formed in each of pixels, the control
apparatus further comprises a quantization unit configured to
quantize the concavo-convex data to N-value (N is an integer of two
or greater) data, the quantization unit quantizes the
concavo-convex data in such a way that an average value of a height
in the concavo-convex data and an average value of a height
indicated by the N-value data are substantially equal in any local
region including a target pixel, and the control unit controls the
forming apparatus based on the N-value data obtained from the
quantization unit.
12. The control apparatus according to claim 11, further comprising
a binary division unit configured to divide the quantized N-value
data into a plurality of pieces of binary division data.
13. The control apparatus according to claim 12, wherein the binary
division unit divides the quantized N-value data into the plurality
of pieces of binary division data in such a way that values of
pixels corresponding to a scanning operation in a later stage are
uniform.
14. The control apparatus according to claim 12, wherein, in a case
where the average value indicated by the N-value data in the any
local region is not an integer, the binary division unit divides
the N-value data into the plurality of pieces of binary division
data in such a way that an ink amount in the any local region is
substantially-equally divided between the plurality of pieces of
binary division data.
15. A control method for controlling a forming apparatus which
forms concavo-convex structure by ejecting ink, comprising the
steps of: obtaining concavo-convex data indicating the
concavo-convex structure to be formed; dividing the concavo-convex
data into a plurality of pieces of data for a plurality of
scanning; and controlling a formation order, performed by the
forming apparatus, of the concavo-convex portions each
corresponding to the plurality of pieces of data divided by the
dividing unit based on a feature amount of the concavo-convex
indicated by the concavo-convex data.
16. Anon-transitory computer readable storage medium storing a
program which performs a control method for controlling a forming
apparatus which forms concavo-convex structure by ejecting ink, the
control method comprising the steps of: obtaining concavo-convex
data indicating the concavo-convex structure to be formed; dividing
the concavo-convex data into a plurality of pieces of data for a
plurality of scanning; and controlling a formation order, performed
by the forming apparatus, of the concavo-convex portions each
corresponding to the plurality of pieces of data divided by the
dividing unit based on a feature amount of the concavo-convex
indicated by the concavo-convex data.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a control apparatus and a
control method for controlling a forming apparatus which forms a
surface having concavo-convex or three-dimensional object.
[0003] 2. Description of the Related Art
[0004] Various methods are known as a method for forming desired
concavo-convex structure and three-dimensional objects. For
example, there are known a method in which a material is carved
with a carving machine or the like and a method in which materials
such as curable resin and gypsum are stacked. Meanwhile, a method
in which an image is printed on a surface of a three-dimensional
object is also known. For example, there are known a method in
which an image is printed on a special sheet in advance by using a
printing apparatus such as an offset printer and the sheet is
pasted onto a target three-dimensional object and a method in which
color materials are ejected directly onto a three-dimensional
object by using an inkjet recording method. Surface characteristics
such as sharpness and smoothness of the shapes of such
concavo-convex and three-dimensional objects greatly affect the
appearance and impression of the concavo-convex and
three-dimensional objects.
[0005] Moreover, Japanese Patent Laid-Open No. 2004-299058
discloses a method of obtaining a hard copy in which
three-dimensional appearance and texture is expressed by performing
concavo-convex formation and image formation substantially at the
same time by using an inkjet method. The following method is
generally employed to express the concavo-convex in the
aforementioned method. The concavo-convex is formed by dividing the
concavo-convex into multiple layers and printing each of the layers
over another layer.
[0006] As described above, the sharpness and smoothness of the
formed concavo-convex greatly affects the appearance of the
outputted object. However, the sharpness and smoothness cannot be
appropriately reproduced by the processing of simply dividing the
concavo-convex structure into multiple layers and printing each of
the layers over another layer.
[0007] For example, in a case where the concavo-convex structure is
formed by performing printing multiple times, steps are sometimes
clearly visible in the concavo-convex layers due to reasons such as
displacement between the layers, spreading of the ink, and
contraction characteristic in curing. If such roughness is formed
in a case where a smooth inclined surface is desired to be
reproduced, smoothness of the inclined surface is lost and a
desired texture cannot be obtained.
[0008] Meanwhile, reproduction of acute angles (for example, a
cross-sectional shape like saw teeth) is sometimes difficult
depending on the surface tension and spreading characteristics of a
material used to form the concavo-convex structure. In this case, a
sharp shadow formed by the concavo-convex of the surface is lost
and a desired texture cannot be obtained.
SUMMARY OF THE INVENTION
[0009] A control apparatus of the present invention configured to
control a forming apparatus which forms concavo-convex structure by
ejecting ink comprises an obtaining unit configured to obtain
concavo-convex data indicating the concavo-convex structure to be
formed, a dividing unit configured to divide the concavo-convex
data into a plurality of pieces of data for a plurality of
scanning, and a control unit configured to control the forming
apparatus based on the plurality of pieces of data. The control
unit controls a formation order, performed by the forming
apparatus, of the concavo-convex portions each corresponding to the
plurality of pieces of data divided by the dividing unit based on a
feature amount of the concavo-convex indicated by the
concavo-convex data.
[0010] Further features of the present invention will become
apparent from the following description of exemplary embodiments
(with reference to the attached drawings).
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a view showing a configuration example of a
concavo-convex forming apparatus in Embodiment 1;
[0012] FIG. 2 is a schematic view showing a halftone expression in
area coverage modulation;
[0013] FIGS. 3A to 3E are views for explaining an operation of
forming concavo-convex or an image;
[0014] FIG. 4 is a view showing an example of cross-sections of a
concavo-convex layer and an image layer formed on a recording
medium;
[0015] FIGS. 5A to 5D are schematic views showing an example of
differences depending on printing conditions in formation of the
concavo-convex layer;
[0016] FIGS. 6A to 6C are flowcharts showing examples of processing
of the concavo-convex forming apparatus in the embodiment;
[0017] FIG. 7 is a schematic view showing an example of blocks
obtained by dividing the concavo-convex data in Embodiment 1;
[0018] FIG. 8 is a schematic view showing pieces of slice data
obtained by dividing the inputted concavo-convex data and examples
of the stacking order determined by processing in Embodiment 1;
[0019] FIG. 9 is a schematic view showing a configuration example
of a head cartridge and an ultraviolet light irradiation device in
Embodiment 2;
[0020] FIGS. 10A and 10B are schematic views showing differences in
formed concavo-convex in a case where the time from ink ejection to
ultraviolet light exposure is varied;
[0021] FIG. 11 is a view showing an example of a quantized ink
amount data and pieces of slice data in Embodiment 3;
[0022] FIGS. 12A to 12D are schematic views showing differences in
the shape of concavo-convex depending on stacking order control in
Embodiment 3;
[0023] FIG. 13 is a flowchart showing an example of processing in
Embodiment 4;
[0024] FIG. 14 is a flowchart showing a detailed example of N-value
processing in Embodiment 4;
[0025] FIGS. 15A to 15D are a view showing a matrix group used in
the N-value processing in Embodiment 4;
[0026] FIG. 16 is a view showing a matrix which is a base of
matrices in FIGS. 15A to 15D;
[0027] FIGS. 17A to 17D are views showing examples of N-value data
generated by performing the N-value processing in Embodiment 4;
[0028] FIG. 18 is a flowchart showing a detailed example of pass
division processing in Embodiment 4;
[0029] FIGS. 19A to 19C are views showing examples of binary
division data generated from the N-value data of FIG. 17D; and
[0030] FIGS. 20A to 20E are views showing examples of results of
pass division in which ratio control in Embodiment 4 is
performed.
DESCRIPTION OF THE EMBODIMENTS
[0031] An embodiment of the present invention is described below
with reference to the drawings. Note that the embodiments described
below do not limit the present invention described in the scope of
claims, and not all of combinations of features described in the
embodiments are necessary for solving method of the present
invention.
Embodiment 1
Schematic Configuration of Concavo-Convex Forming Apparatus
[0032] FIG. 1 is a view showing a configuration example of a
concavo-convex forming apparatus in the embodiment. An inkjet
printer configured to record concavo-convex and images by using
inks is described as an example of the concavo-convex forming
apparatus 100. A head cartridge 101 has a recording head including
multiple ejection ports and an ink tank configured to supply the
inks to the recording head. Moreover, the head cartridge 101 is
provided with a connector for receiving signals for driving the
ejection ports of the recording head and the like.
[0033] For example, in the ink tank, total of six types of inks
including a liquid resin ink used to form an concavo-convex layer
and color inks of cyan, magenta, yellow, black, and white used to
form an image layer are independently provided. For example, an
ultraviolet curable ink is used as the liquid resin ink. The head
cartridge 101 is aligned and mounted on a carriage 102 to be
replaceable, and the carriage 102 is provided with a connector
holder for transmitting drive signals and the like to the head
cartridge 101 via the connector. Moreover, an ultraviolet light
irradiation device 115 is mounted on the carriage 102 and is used
to cure the ejected curable ink and fix the ink onto a recording
medium.
[0034] The carriage 102 can reciprocate along guide shafts 103.
Specifically, a main scanning motor 104 serving as a drive source
drives the carriage 102 via drive mechanisms such as a motor pulley
105, a driven pulley 106, and a timing belt 107, and the position
and movement of the carriage 102 is controlled. This movement of
the carriage 102 along the guide shafts 103 is referred to as "main
scanning," and the movement direction is referred to as "main
scanning direction."
[0035] Recording media 108 such as print sheets are placed on an
auto sheet feeder (hereafter, referred to as "ASF") 110. In image
recording, pickup rollers 112 are rotated by drive of a sheet
feeding motor 111 via gears, and the recording media 108 are
separated from one another to be fed one by one from the ASF 110.
Then, each of the recording media 108 is conveyed by rotation of a
conveyance roller 109 to a recording start position at which the
recording medium 108 faces an ejection port surface of the head
cartridge 101 on the carriage 102. A line feed (LF) motor 113
serving as a drive source drives the conveyance roller 109 via
gears.
[0036] Determination on whether the recording medium 108 is fed and
final determination on the position of the recording medium 108 in
the feeding is made at the time the recording medium 108 passes a
paper end sensor 114. The head cartridge 101 mounted on the
carriage 102 is held such that the ejection port surface protrudes
downward from the carriage 102 and is parallel to the recording
medium 108. A control unit 120 is formed of a CPU, a ROM, a RAM,
and the like. The control unit 120 receives concavo-convex data
indicating concavo-convex structure and image data and controls
operations of various parts of the concavo-convex forming apparatus
100, based on the received data.
(Concavo-Convex Recording Operation and Image Recording
Operation)
[0037] Description is given below of a concavo-convex recording
operation and an image recording operation in the inkjet printer
having the configuration shown in FIG. 1. First, the recording
medium 108 is conveyed to a predetermined recording start position.
Then, the carriage 102 is moved above the recording medium 108
along the guide shafts 103 and the inks are ejected from the
ejection ports of the recording head while the carriage 102 is
moved. The ultraviolet light irradiation device 115 delivers
ultraviolet light along with the movement of the recording head to
cure the ejected ink and fix the ink onto the recording medium.
Then, at the point where the carriage 102 reaches one ends of the
guide shafts 103, the conveyance roller 109 conveys the recording
medium 108 by a predetermined amount in a direction perpendicular
to the scanning direction of the carriage 102. This conveyance of
the recording medium 108 is referred to as "sheet feeding" or
"sub-scanning" and the direction of this conveyance is referred to
as "sheet feeding direction" or "sub-scanning direction." After the
conveyance of the recording medium 108 by the predetermined amount
is completed, the carriage 102 is moved again along the guide
shafts 103. Concavo-convex is formed on the entire recording medium
108 by repeating the scanning of the carriage 102 of the recording
head and the sheet feeding as described above. After the
concavo-convex is formed, the conveyance roller 109 returns the
recording medium 108 to the recording start position and an image
is formed on the concavo-convex by a process similar to that of the
concavo-convex formation. Although the formation of the
concavo-convex and the formation of the image is performed
separately in the above description to simplify the explanation, it
is possible to perform processing in which the order of ejecting
the respective types of inks in each scanning operation is
controlled such that the image layer is formed on the
concavo-convex layer, and no returning of the recording medium is
performed. Moreover, the concavo-convex layer may be formed after
the image layer is formed.
[0038] FIG. 2 is a schematic view showing expressions of images
which are controlled through area coverage modulation. The
expression of images are achieved basically by performing binary
control in which whether the recording head ejects an ink droplet
is determined. In the embodiment, on-off control of the ink is
performed for each of pixels defined for an output resolution of
the concavo-convex forming apparatus, and a state where all of
pixels in a unit area are set to ON is treated as an ink amount of
100%. In a so-called binary printer like one described above, only
an ink amount of 100% or 0% can be expressed in one pixel.
Accordingly, a halftone is expressed by a group of multiple pixels.
In the examples shown in FIG. 2, instead of performing halftone
expression in a density of 25% as in a lower left portion of FIG.
2, the ink is ejected to four pixels out of 4.times.4 pixels as in
a lower right portion of FIG. 2 to express 4/16=25% in terms of
area. Other tones can be expressed in a similar way. Note that the
total number of pixels, patterns of pixels set to ON, and the like
for expressing a halftone are not limited to those in the examples
described above. Error diffusion processing and the like are
popularly used.
[0039] In the concavo-convex formation of the embodiment, height
control is performed for each position by using the concept of the
ink amount described above. In a case where a substantially-uniform
layer is formed at the ink amount of 100% in the concavo-convex
formation, the layer has a certain thickness=height corresponding
to the volume of the ejected ink. For example, in a case where a
layer formed at the ink amount of 100% has a thickness of 20 .mu.m,
the thickness of 100 .mu.m can be reproduced by stacking the layer
five times. In other words, the amount of ink to be ejected to a
position requiring a height of 100 .mu.m is 500%. Note that, in a
case where there is a layer in which the ink amount does not reach
100%, for example, in a case of forming a layer having a thickness
of 10 .mu.m, the ink may be ejected such that the ink amount of 50%
is achieved in terms of area as described in FIG. 2.
[0040] FIGS. 3A to 3E are views for explaining an operation for
forming concavo-convex or an image by causing the recording head to
scan above the recording medium 108. Image recording of a region
having a width equal to the width L of the recording head is
performed with the main scanning of the carriage 102, and the
recording medium 108 is conveyed by the distance L in the
sub-scanning direction every time recording of one line is
completed. To simplify the explanation, it is assumed that the
concavo-convex forming apparatus in the embodiment can only perform
ink ejection up to the ink amount of 100% in one scanning operation
and, in a case of performing concavo-convex formation exceeding the
ink amount of 100%, the scanning is performed multiple times on the
same region without performing the conveyance. For example, in a
case where the maximum ink amount to be ejected is 500%, the same
line is scanned five times. This is explained by using FIGS. 3A and
3B. After a region A is scanned five times by the recording head
(FIG. 3A), the recording medium 108 is conveyed in the sub-scanning
direction and the main scanning is repeated five times for a region
B (FIG. 3B).
[0041] Multiple times of scanning or so-called multi-pass printing
is sometimes performed even in a case where the ink amount is 100%
or less, to suppress image deterioration such as periodic
concavo-convex due to the accuracy of the recording head. An
example of two-pass recording is shown in FIGS. 3C to 3E. In this
example, image recording of a region having a width equal to the
width L of the recording head is performed with the main scanning
of the carriage 102, and the recording medium 108 is conveyed by
the distance L/2 in the sub-scanning direction every time recording
of one line is completed. Recording in the region A is performed in
the m-th main scanning operation (FIG. 3C) and the (m+1)th main
scanning operation (FIG. 3D) of the recording head. Meanwhile,
recording in the region B is performed in the (m+1)th main scanning
operation (FIG. 3D) and the (m+2)th main scanning operation (FIG.
3E) of the recording head. Although description is given herein of
the operations in the two-pass recording, the number of passes
performed for recording can be changed depending on the desired
quality and concavo-convex accuracy of an image to be recorded. In
a case of performing n-pass recording, for example, the recording
medium 108 is conveyed by the distance of L/n in the sub-scanning
direction every time the recording of one line is completed. In
this case, even if the ink amount is 100% or less, concavo-convex
or an image is formed by dividing the concavo-convex or the image
into multiple print patterns and causing the recording head to
perform main scanning n-times on the same line of the recording
medium. In the embodiment, in order to avoid confusion between the
scanning for the aforementioned multi-pass printing and the
scanning for ejecting the ink at an ink amount of 100% or greater,
description is given assuming that the multi-pass printing is not
performed and multiple times of scanning is performed to stack
layers. Note that description that the multi-pass printing is not
performed is given to avoid confusion, and a mode in which the
multi-pass printing is performed can be employed as a matter of
course.
[0042] In an inkjet printer, if the distance from the recording
head to the recording medium is inappropriate, ink droplets are
affected by air currents and the like and the landing position
accuracy of the ink droplets sometimes cannot be maintained or the
ink droplets sometimes do not adhere to the recording medium and
scatter inside the apparatus. In a case of forming a shape in which
the difference between a convex and a concave is great, an
appropriate distance cannot be maintained. Accordingly, there is
generally a limit to the height of the concavo-convex. In a case
where the height exceeds the limit, clipping and compression is
sometimes performed for an amount exceeding the height limit.
Description is given assuming that the concavo-convex data handled
in the embodiment has been already subjected to such
processing.
[0043] Moreover, in the embodiment, the recording medium is not
limited to a particular medium. Media made of various materials
such as paper and plastic film are usable as long as the media can
be subjected to the image recording by the recording head.
[0044] FIG. 4 is a cross-sectional view of the concavo-convex layer
for forming concavo-convex structure and the image layer for
coloring which are formed on the recording medium. In the
embodiment, description is given assuming that the image layer is
formed on a surface of the concavo-convex layer whose height
distribution is about 1 mm. Strictly speaking, the image layer also
has a height distribution. However, since the thickness of the
image layer is about several .mu.m, an effect on the final
concavo-convex is small and can be ignored. As a matter of course,
it is possible to perform processing of correcting height data and
the like in consideration of the thickness distribution of the
image layer.
(Difference in Output Characteristics Depending on Method of
Forming Concavo-Convex Layer)
[0045] FIGS. 5A to 5D are schematic views showing differences
depending on printing conditions in the formation of the
concavo-convex layer. In the embodiment, description is given of an
example in which so-called slice data is generated by dividing the
concavo-convex data for a plurality of layers and the ink is
ejected based on the slice data. The slice data of the embodiment
is data in which information indicating, for example, the height on
a two-dimensional xy plane is arranged for each pixel as in the
concavo-convex data. For example, the slice data is generated for
each of layers with the height of a layer formable in one scanning
operation being set as the upper limit. In other words, multiple
pieces of slice data indicating the heights of the respective
layers are generated by dividing the concavo-convex data for each
scan.
[0046] FIG. 5A is a method generally used in concavo-convex
formation by way of stacking. The method of FIG. 5A is a method in
which the inputted concavo-convex data is divided along contour
lines to generate pieces of slice data, and layers of ink are
stacked up from an ink layer corresponding to a lower layer in the
data and become higher as the number of times of scanning
increases. Meanwhile, FIG. 5B shows a method as follows. Data is
divided along lines in each of which the distance from the surface
of an concavo-convex face (upper two sides of each triangle in the
drawing) in a direction toward the recording medium surface is the
same at any point on the line, and a layer corresponding to data
close to the concavo-convex surface is formed in a later scanning
operation. In a case where the aforementioned pieces of data are
converted into an ink amount per unit area which is required on
each xy plane, the data for the uppermost layer subjected to
division in the method of FIG. 5B is the same as the slice data for
the lowermost layer generated in FIG. 5A. In other words, the
pieces of data subjected to division in FIG. 5B are equivalent to
the pieces of slice data generated in the method of FIG. 5A which
are rearranged such that the stacking order thereof is reversed. To
put it differently, FIG. 5B is an example in which the scanning
order is changed such that the slice data for a lower layer is
recorded in scanning of a later stage and the slice data for an
upper layer is recorded in scanning of an earlier stage.
[0047] The total amount of ink to be ejected in FIG. 5A is the same
as that of FIG. 5B. However, the amount of ink stacked in each
scanning operation is different in FIGS. 5A and 5B. Due to this
difference, the shape of concavo-convex to be finally formed
sometimes varies. Examples of the shapes of concavo-convex
outputted by the stacking methods of FIGS. 5A and 5B are shown in
FIGS. 5C and 5D, respectively.
[0048] The ejected ink is irradiated with ultraviolet light from
the ultraviolet light irradiation device and is cured in each
scanning operation. Droplets of the ejected ink do not have fixed
shapes such as rectangular solids which can be digitally stacked
up. The droplets thus spreads on the recording medium or a
concavo-convex layer formed in the previous scanning operation.
Moreover, the droplets are cured by being irradiated with
ultraviolet light while spreading. The shapes of the cured ink
droplets are affected by the physical properties and shape of the
layer under the droplets, the timing of curing, and the like.
[0049] In FIG. 5C, the area of a layer formed by a scanning
operation in a later stage is equal to or smaller than the area of
a lower layer. Accordingly, steps are formed between the layers.
Meanwhile, in FIG. 5D, a layer formed by a scanning operation in a
later stage is formed by ejecting the ink in terms of area equal to
or larger than the area of a lower layer, and thereby covers the
lower layer to form relatively-smooth inclined surfaces.
[0050] Observing the aforementioned differences in shapes from the
view point of the height of concavo-convex and the sharpness of a
convex portion, a decrease of the height is small in FIG. 5C
because the amount of ink flowing down is relatively small.
Moreover, in FIG. 5C, the deterioration in the angle (spreading) of
a top portion of the inputted triangular concavo-convex data is
relatively small, and the method of FIG. 5C is advantageous in many
cases. Meanwhile, in FIG. 5D, since the ink of an upper layer
covers a lower layer and the amount of ink flowing down is
relatively large, the height becomes lower than that of FIG. 5C.
Moreover, although relatively smooth inclined surfaces with few
steps are formed in FIG. 5D, the angle of the top portion is
deteriorated.
[0051] As described above, concavo-convex characteristics such as
smoothness and sharpness depend on material properties and
formation processes. Accordingly, in the embodiment, away in which
layers of ink are stacked is controlled based on characteristics
(smooth concavo-convex structure is suitable or sharp
concavo-convex structure is suitable) of concavo-convex expressed
by the inputted concavo-convex data.
[0052] As described above, the slice data is data indicating the
height of each layer, and is generated for each layer. For example,
in a case where a layer formed at the ink amount of 100% has a
thickness of 20 .mu.m, the upper limit of the height is 20 .mu.m in
the slice data for one layer. In this case, the slice data for one
layer includes a pixel of 20 .mu.m, a pixel of 0 .mu.m, and a pixel
of 10 .mu.m. In other words, multiple levels of height can exist in
the slice data for one layer. Since the multiple levels of height
in the sliced layer for one layer is controlled by on and off of
ink droplets, stochastic control is actually performed as described
by using FIG. 2. Specifically, controlling multiple levels of
height in an area enables ejection of ink droplets corresponding to
multiple levels of heights. In a case where an ink which spreads
widely is used, such control leads to reduction of concavo-convex
in units of pixels, and the levels of height are averaged among
multiple pixels. Accordingly, multiple levels of heights can be
expressed in units of multiple pixels. Meanwhile, in a case where
an ink which does not spread widely is used, such control may cause
unintended concavo-convex on the surface, i.e. roughness. In order
to avoid this, it is possible to use a method in which binarization
processing is performed for each piece of slice data without
performing halftone processing in the concavo-convex formation and
the height is controlled based only on the number of stacked
layers. In the embodiment, description is given of an example in
which the halftone processing (area coverage modulation processing)
is performed in the concavo-convex formation. In Embodiment 3 to be
described later, description is given of a method in which the
binarization processing is performed for each piece of slice data
without performing the halftone processing in the concavo-convex
formation and the height is controlled based only on the number of
stacked layers.
(Flow of Concavo-Convex Layer Formation)
[0053] FIGS. 6A to 6C are views showing flowcharts. FIG. 6A is a
flowchart showing an operation of the concavo-convex forming
apparatus in the embodiment. For example, the operation of this
flowchart is implemented by causing the CPU to execute a program
stored in the not-illustrated ROM forming the control unit 120.
[0054] First, in step S601, the control unit 120 obtains the
concavo-convex data which is a set of information on the height at
each set of coordinates x, y.
[0055] Next, in step S602, the control unit 120 converts the
concavo-convex data obtained in step S601 to an ink amount in each
pixel and divides the converted data into pieces of data at
predetermined contour lines. Hereafter, each of the pieces of data
obtained by dividing the concavo-convex data is referred to as
slice data. The intervals of the contour lines correspond to the
upper limit of the height in the slice data, i.e. the ink amount of
100%.
[0056] Then, in step S603, the control unit 120 divides the
concavo-convex data obtained in step S601 into blocks of a
predetermined size on the xy plane. FIG. 7 is a schematic view
showing the concavo-convex data and the blocks obtained by the
division. Determination on "which one of sharpness and smoothing is
to be prioritized in the concavo-convex to be formed" and control
based on this determination, which is to performed in the following
steps, is performed in units of the blocks obtained by the division
in step S603. In this case, the output resolution of the
concavo-convex formation is set to 600 dpi, and blocks each having
a size of 128 pixels by 128 pixels are used. The size of the blocks
is not limited to this and can be set as appropriate to a size of m
pixels by m pixels corresponding to a size of several mm to 1 cm
square in the output. The shape of the blocks may be a shape other
than a quadrate, as a matter of course.
[0057] Next, in step S604, the control unit 120 determines a
feature amount of the concavo-convex indicated by the
concavo-convex data, for each of the blocks obtained by the
division in step S603. For example, the control unit 120 determines
the degree of sharpness. In this case, the control unit 120 applies
a Laplacian filter to the divided two-dimensional concavo-convex
data, and determines whether the priority is given to sharpness or
smoothness in this region by comparing the data with a
predetermined threshold. For example, the control unit 120
determines that an edge portion is a sharpness prioritized region
and a non-edge portion is a smoothness prioritized region. Then, as
will be described later, operations to be performed are switched
between an operation for a region having a predetermined feature
amount and an operation for a region having a feature amount other
than the predetermined feature amount.
[0058] The method of steps S603 and S604 is one of methods for
determining which one of sharpness and smoothing is to be
prioritized in each of predetermined regions, and many methods
other than the one described above are conceivable. For example, a
frequency component may be used. Sharpness may be detected by
using, for example, a method in which Fourier transform or the like
is utilized to extract only the high-frequency components.
Moreover, instead of dividing the data into rectangular regions,
the region division can be performed by using a range of a certain
distance from the extracted high-frequency components on the real
space as a mask.
[0059] In step S605, the control unit 120 determines the stacking
order of the pieces of slice data generated by dividing the
concavo-convex data in step S602, based on the degree of sharpness
determined in step S604. FIG. 6B is a flowchart showing an example
of an operation performed in step S605. Here, a case where the
inputted concavo-convex data is data for N layers is given as an
example. In other words, concavo-convex indicated by the
concavo-convex data can be formed by stacking N layers. Description
is given of an example in which the concavo-convex indicated by the
data for N layers is formed by performing the main scanning N+1
times. Refer also to FIG. 8. In this example, assuming that there
is slice data to be used in the n-th main scanning operation, n is
the scanning number of this slice data. The processing of FIG. 6B
is performed for each of the blocks obtained by the division in
step S603.
[0060] In step S611, the control unit 120 determines whether a
target block is a sharpness prioritized block. This determination
is performed based on the detection result of sharpness obtained in
step S604. In a case where the target block is a sharpness
prioritized block, in step S612, the control unit 120 sets up the
slice data such that the slice data for the uppermost layer in the
target block is recorded in the (N+1)th main scanning operation.
Specifically, the control unit 120 sets the scanning number of the
slice data for the uppermost layer in the target block to n+1, so
that the slice data for the uppermost layer is recorded in the last
scanning operation. Then, the control unit 120 sequentially
determines the scanning numbers of other pieces of slice data, from
the slice data used in a main scanning operation in a later stage
(upper layer), like n=N, N-1, . . . , 1. The slice data used in the
n-th main scanning operation is lowermost-layer slice data out of
pieces of slice data whose scanning numbers are not determined yet.
This operation is repeated until the scanning numbers are
determined for all pieces of slice data. In other words, in steps
S613 and S614, the control unit sets up the concavo-convex forming
apparatus such that the lowermost-layer slice data out of pieces of
slice data whose scanning numbers are not determined yet is
recorded in the n-th scanning operation corresponding to a scanning
operation in a later stage. If the processing for all pieces of
slice data are not completed in step S615, n is decremented and the
processing returns to step S614.
[0061] In a case where the target block is not a sharpness
prioritized block in step S611, similar processing is performed
with the processing of determining the slice data for the (N+1) th
main scanning operation in step S612 being omitted.
[0062] In the processing of FIG. 6B, in a block in which the
priority is given to the degree of sharpness, the slice data for
the uppermost layer which is a sharp portion is recorded in the
last scanning operation. Accordingly, concavo-convex in which the
sharpness is maintained can be formed. Meanwhile, regarding the
pieces of slice data for layers other than the uppermost layer, the
slice data for a lower layer is set to be recorded in a main
scanning operation in a later stage. Accordingly, it is possible to
form concavo-convex with a high degree of smoothness in which steps
are eliminated. In other words, it is possible to form
concavo-convex which has both of a high degree of sharpness and a
high degree of smoothness.
[0063] Meanwhile, in a block in which the priority is not given to
the degree of sharpness (i.e. a block in which the priority is
given to the degree of smoothness), the slice data for a lower
layer is set to be recorded in a main scanning operation in a later
stage. Accordingly, it is possible to form concavo-convex with a
high degree of smoothness in which steps are eliminated.
[0064] After the stacking order of the pieces of slice data is
determined as described above for all blocks, in step S606, the
control unit 120 performs quantization (binarization) by which on
and off of the ink for each pixel is determined. Specifically, a
value (FIG. 2) controlled through the area coverage modulation and
corresponding to the ink amount indicated in data for each block is
allocated to each pixel. Such quantization processing is performed
in each block for each piece of slice data. Note that the area
coverage modulation processing may be performed in each of blocks
obtained by the division in step S603 or each of sub-blocks
obtained by further dividing the block.
[0065] Next, in step S607, the control unit 120 performs
concavo-convex formation based on the stacking order determined in
step S605 and the binary data indicating on and off of the ink and
determined in step S606. For example, in a case where the binary
data to be used in a certain main scanning operation includes a
block in which the stacking order is changed, the binary data after
the stacking order change is used for this block. Moreover, an
image can be printed on the formed concavo-convex as needed.
[0066] FIG. 8 is a schematic view showing pieces of slice data
obtained by dividing the inputted concavo-convex data with N=3
being satisfied and the stacking order determined by the processing
described above. Concavo-convex portions 801, 802, and 803 of FIG.
8 are processing examples of blocks which are determined to be
sharpness prioritized blocks in step S604. In each of these blocks,
the slice data for the uppermost layer is recorded in the last main
scanning operation to prevent deterioration of sharpness at an apex
of a triangle. Moreover, layers below the uppermost layer are
stacked in such a way that steps are less visible. Meanwhile,
concavo-convex portions 804, 805, and 806 of FIG. 8 in which the
priority is not given to the degree of sharpness do not have shapes
desired to be reproduced with sharpness maintained as in an apex of
a triangle. In other words, the concavo-convex portions 804, 805,
and 806 are in regions outside regions of sharp portions.
Accordingly, in these portions, the slice data for a layer having a
larger area is set to be formed in a main scanning operation in a
later stage, and smooth concavo-convex in which steps are less
visible are formed.
[0067] In the flowchart of FIG. 6B and the example of the
concavo-convex portion 801 in FIG. 8, description is given of the
example in which, in the sharpness prioritized block, the slice
data for the uppermost layer is recorded in the last scanning
operation, and pieces of slice data for layers other than the
uppermost layer are recorded such that slice data for a lower layer
is recorded in a main scanning operation performed in a later
stage. However, the recording operation is not limited to this
example. For example, in the sharpness prioritized block, the
pieces of slice data can be recorded sequentially from slice data
for a lower layer by performing main scanning operations. In other
words, in the example of the concavo-convex portion 801 in FIG. 8,
the order of the N-th pass and the (N-1)th pass may be
interchanged. Moreover, the recording order of pieces of slice data
for layers other than the uppermost layer in the sharpness
prioritized block may be changed as necessary depending on the
degree of spreading of the ink.
[0068] As described above, the concavo-convex forming apparatus of
the embodiment is capable of forming a suitable concavo-convex
shape by controlling a formation pattern for each block depending
on the sharpness of the inputted concavo-convex data.
[0069] In the embodiment, description is given of the method for
controlling the stacking order of the pieces of slice data
depending on the degree of sharpness of the concavo-convex.
However, a method in which the control of the stacking order of the
pieces of slice data is achieved simply by changing the stacking
order to the ascending or descending order of the area is
conceivable.
[0070] Moreover, in the embodiment, the concavo-convex data is
converted into pieces of slice data by using contour lines
corresponding to the ink amount of 100%. However, a method of
dividing the concavo-convex at lines corresponding to an ink amount
of less than 100% is conceivable. Furthermore, instead of using
contour lines, the ink amount at which the concavo-convex data is
divided may vary among positions.
[0071] Moreover, the correspondence between the slice data and the
scanning number are not limited to the example shown in FIGS. 6B
and 8. In the embodiment, regarding the characteristics of the
concavo-convex to be finally formed, the order of stacked layers is
important and there is no need to assign specific scanning numbers
to the respective pieces of slice data. For example, in blocks such
as the concavo-convex portions 803 and the concavo-convex portion
806 of FIG. 8, the formation thereof may be performed in a scanning
operation of any number. Moreover, although the concavo-convex
portions 801, 802, and 803 of FIG. 8 shows examples in which the
slice data for the uppermost layer is formed in the (N+1)th pass,
it is possible to shift the entire formation operation by one pass
and form the slice data for the uppermost layer in the N-th
pass.
[0072] In the embodiment, the concavo-convex data is described to
be divided into multiple pieces of slice data in advance to
simplify the explanation. However, the method of the present
invention is not limited to this. For example, a method may be
employed in which subtraction from the concavo-convex data stored
in the control unit 120 is performed every scanning operation.
[0073] Moreover, in the embodiment, description is given of the
stacking order of pieces of slice data and the method in which the
total amount of the ink in the slice data is not changed, i.e. the
method in which the volume is maintained. However, the method of
the present invention is not limited to this. For example, in a
case of covering a lower layer in a main scanning operation in a
later stage as in FIG. 5D, a desired height sometimes cannot be
obtained. In such a case, the height of the concavo-convex to be
formed may be compensated by performing control of ejecting a
greater amount of ink. Moreover, it is possible to perform
processing of compensating the degree of sharpness by forming
portions of concavo-convex on the entire surface of the recording
medium as in FIG. 5D and then forming only sharp portions (for
example, convex portions such as an apex of a triangle) in the last
main scanning operation.
[0074] Moreover, although the order of formation is controlled
depending on the degree of sharpness of the concavo-convex data in
the embodiment, it is possible to employ a method for controlling
the order based on other feature values such as the degree of
importance of height accuracy, the degree of importance of
inclination angle accuracy, color and frequency of an image to be
printed on a surface, and the like.
Embodiment 2
[0075] In Embodiment 1, description is given of the method in which
the surface characteristics of the concavo-convex to be formed are
controlled by dividing the concavo-convex into multiple layers and
changing the way of stacking the layers as the operation condition
of the concavo-convex formation. In the embodiment, description is
given of a method in which the surface characteristics of the
concavo-convex is controlled by controlling the illumination
intensity and timing of an ultraviolet light irradiation device as
the operation condition of the concavo-convex formation. Note that
the configurations and operations of a concavo-convex forming
apparatus in the embodiment are the same as those shown in
Embodiment 1 unless otherwise noted, and description thereof is
thus omitted.
[0076] FIG. 9 is a schematic view showing configurations of the
head cartridge 101 and an ultraviolet light irradiation device 915
in the embodiment. The head cartridge 101 and the ultraviolet light
irradiation device 915 are fixed to the carriage 102 and perform
ejection of inks and ultraviolet light irradiation while moving in
the direction of the arrow in the drawing in print scanning. The
ultraviolet light irradiation device 915 includes two light
emitting portions. The distance to the head cartridge 101 is
different between the two light emitting portions. The time from
the ink ejection to the ultraviolet light exposure is different
between the light emitting portion 915a at a position close to the
head cartridge 101 and the light emitting portion 915b at a
position farther away from the head cartridge 101.
[0077] FIGS. 10A and 10B are schematic views showing differences in
formed concavo-convex in a case where the time from the ink
ejection to the ultraviolet light exposure is varied. FIG. 10A
shows an example of a case where the time from the ejection to the
exposure is relatively short and FIG. 10B shows an example of a
case where the time from the ejection to the exposure is relatively
long. Ink droplets ejected from the recording head come into
contact with the recording medium or ink of a lower layer and then
spread. In the example of FIG. 10A, the ink is cured before
sufficiently spreading. Accordingly, the height of the ink is great
but steps are likely to be formed. Meanwhile in the example of FIG.
10B, the ink is cured after spreading to some extent. Accordingly,
the height of the ink is not great but steps are less likely to be
formed.
[0078] Next, description is given of an operation of the
concavo-convex forming apparatus in the embodiment by using FIG.
6C. Since steps S651 to S654 are the same operations as steps S601
to S604 in Embodiment 1, description thereof is omitted.
[0079] In step S655, the control unit 120 determines an exposure
intensity and an exposure timing in concavo-convex output performed
in step S656 of a later stage, for each of blocks obtained by
division in step S653, based on the degree of sharpness determined
in step S654. Ina case where the priority is given to the degree of
sharpness in step S654, the exposure is performed immediately after
the ejection by using the light emitting portion 915a for a
corresponding block. Meanwhile, in a case where the priority is not
given to the degree of sharpness, the exposure is performed after a
certain time elapses from the ejection by using the light emitting
portion 915b for the corresponding block. In the embodiment, the
stacking order of the pieces of slice data may be the same in all
of the blocks.
[0080] As described above, the concavo-convex forming apparatus of
the embodiment can form a suitable concavo-convex shape by
controlling ink curing for each block depending on the sharpness of
the inputted concavo-convex data.
[0081] In the embodiment, description is given of the method in
which the light emitting timings of the two light emitting portions
are controlled. However, it is possible to form the light emitting
portions with a light emitting element array capable of controlling
the light amount of each position and use a method in which the
light emitting timing at each position in the array is controlled.
Moreover, it is also possible to perform multi-value control by
controlling the intensity of the two light emitting portions in
multiple levels and controlling the ratio between the two light
emitting portions.
[0082] Moreover, in the embodiment, description is given of the
method in which the light emitting timings are controlled by using
the two light emitting portions. However, a method using only one
light emitting unit can be employed. In this method, the exposure
is performed in a scanning operation different from that for the
ink injection, and the time and the like for curing is controlled
by controlling the timing of this scanning operation.
[0083] Furthermore, in the embodiment, description is given of the
control of the surface characteristics of concavo-convex achieved
by controlling the intensity of the emitted light and the timing of
light emission by the ultraviolet light irradiation device.
However, similar effects can be also obtained by using multiple
types of inks with different ink characteristics such as viscosity,
thixotropic property, and curing rate.
[0084] For example, the following method may be employed. Two types
of inks of an ink C11 with high viscosity and an ink C12 with low
viscosity are used as the ink for concavo-convex formation stored
in the head cartridge 101. In the concavo-convex formation, an
usage ratio between the inks is controlled depending on the degree
of sharpness of the concavo-convex data and the like in such a way
that a great amount of the ink C11 is used in a case where the
priority is given to the degree of sharpness and a great amount of
the ink C12 is used in a case where the priority is given to the
degree of smoothness.
[0085] Moreover, a method can be employed in which the control of
the stacking method described in Embodiment 1 and the control of
the curing timings and the ink types described in Embodiment 2 are
combined to control the surface characteristics of the outputted
concavo-convex depending on the feature value of the concavo-convex
data.
Embodiment 3
[0086] In Embodiment 1, description is given assuming that the
pieces of slice data to be stacked are pieces of multi-value data
in the method in which the surface characteristics of the
concavo-convex to be formed are controlled by dividing the
concavo-convex into multiple layers and changing the way the layers
are stacked. In the embodiment, description is given of an example
for a shaping method in which, for example, multi-value expression
in a layer is not possible. In other words, in the embodiment,
description is given of an example using binarized slice data.
[0087] Configurations and operations of a concavo-convex forming
apparatus in the embodiment are the same as those shown in
Embodiment 1, except for the point that binarization processing is
performed on the concavo-convex data in step S602.
[0088] In the embodiment, the control unit 120 receives, from the
outside, concavo-convex data h(x, y) which is a set of information
on the height at each set of coordinates x, y, and then generates
binarized slice data. For example, the control unit 120 converts
the concavo-convex data h(x, y) into an ink amount I(x, y) by using
a formula (1)
I(x,y)=k.times.h(x,y) formula (1)
[0089] In this formula, k is a coefficient expressing a
relationship between the height and the ink amount. The ink amount
I of 100% is equal to 1.0 as described in Embodiment 1 and
corresponds to the thickness of one layer. For example, in a
concavo-convex forming apparatus in which the thickness of one
layer is 20 .mu.m, k is 1/20 .mu.m. In a case where the
concavo-convex data of the height of 50 .mu.m is inputted in this
apparatus, the ink amount I is 2.5.
[0090] Next, the ink amount converted by using the formula [0091]
(1) is quantized in units of layer thickness by using, for example,
a formula (2) I' (x, y)=floor (I(x, y)) formula (2)
[0092] In this formula, floor is a function for performing
rounding-off in a negative direction. For example, in a case where
the inputted ink amount I is 2.5, the ink amount is rounded off to
2. Although the ink amount is rounded off in the negative direction
in the aforementioned quantization processing, a method in which
the ink amount is rounded off in a positive direction or to the
closest integer can be employed.
[0093] That is the differences from the operation of Embodiment
1.
[0094] FIG. 11 is a view in which examples of a quantized ink
amount I' of 1.times.7 pixels and divided pieces of slice data are
expressed in a matrix. The slice data for the lowermost layer is
assumed to be slice data 1.
[0095] FIGS. 12A to 12D are schematic views showing differences in
the shape of concavo-convex depending on the control of the
stacking order of the pieces of slice data shown in FIG. 11. In
FIGS. 12A and 12B, the types of shades used to hatch the blocks
indicate the scanning operations in which the blocks are formed:
the darker the shade is, the later the scanning operation is
performed. FIG. 12A shows an example in which the slice data 1 for
the lowermost layer is formed in the first scanning operation and
the slice data 4 for the upper most layer is formed in the fourth
scanning operation, and shows a generally-used method in which the
concavo-convex is formed from slice data for a lower layer and
patterns of smaller areas are stacked up. Meanwhile, FIG. 12B shows
a method in which the slice data 4 for the uppermost layer is used
in the first scanning operation and a pattern of a large area
corresponding to the slice data 1 is formed later to cover the
other patterns. FIGS. 12C and 12D are schematic views showing the
shapes of concavo-convex formed by the stacking methods of FIGS.
12A and 12B, respectively. In the examples of FIGS. 12A to 12D, the
concavo-convex of FIG. 12D has better smoothness but decrease in
height is more apparent in FIG. 12D due to the same reasons as
those in the concavo-convex shapes shown in FIGS. 5A to 5D. As
described above, it is possible to control the surface
characteristics of a concavo-convex shape by controlling the
stacking order by using quantized concavo-convex data, i.e. a
pattern binarized in the slice data. Moreover, since determination
of the degree of sharpness and the like can be performed based on
the concavo-convex data before quantization even if the ink amount
after the quantization is the same, more preferable concavo-convex
reproduction can be performed also in a shaping method in which
multi-level expression cannot be performed in a layer.
Embodiment 4
[0096] In Embodiment 1, description is given of the example in
which the processing shown in the flowchart of FIG. 6A is performed
in a case of performing the control of the area coverage
modulation. Specifically, description is given of the example in
which pieces of slice data are generated by dividing the inputted
concavo-convex data and then a pattern (binary data indicating on
and off of the ink) controlled through the area coverage modulation
is assigned to each piece of slice data having a thickness
corresponding to the ink amount of 25%, 50%, or the like.
[0097] In the embodiment, the inputted concavo-convex data is not
divided into pieces of slice data. Instead, N-value processing of
determining the number of times of ink ejection is performed on the
concavo-convex data, and then processing (binarization) of
allocating N-value data to each pass is performed. Specifically, in
Embodiment 1, division into pieces of data (slice data) for
respective passes is performed in the stage of the concavo-convex
data. Meanwhile, in the embodiment, the number of times of ink
ejection for each pixel is determined from the concavo-convex data
and then at which pass the ink is to be ejected is determined
later. In this description, N is an integer equal to or greater
than two.
[0098] FIG. 13 is a flowchart in the embodiment. The processing of
FIG. 13 is also implemented by causing the CPU forming the control
unit 120 to read and execute a program stored in the
not-illustrated ROM. In the embodiment, description is given of a
case where concavo-convex of less than 16 layers (ink amount of
less than 1600%) is formed.
[0099] First, in step S1301, the control unit 120 receives the
concavo-convex data which is a set of information on the height at
each set of coordinates x, y, from the outside. The concavo-convex
data is assumed to be written in 8-bits (0, 1, . . . , 255). In the
concavo-convex data, the thickness of one layer is coded in 16
levels. For example, in a case where a layer formed at the ink
amount of 100% has a thickness of 20 .mu.m, 4 indicates a thickness
of 5 .mu.m, 8 indicates a thickness of 10 .mu.m, 16 indicates a
thickness of 20 .mu.m, 24 indicates a thickness of 30 .mu.m. 256
levels can be expressed in 8-bit data up to layers less than 16
layers.
[0100] Next, in step S1302, the control unit 120 performs
processing of converting the inputted concavo-convex data into the
number of times of ink ejection for each pixel. FIG. 14 is a
flowchart showing details of processing in step S1302. First, in
step S1402, the control unit 120 reads the concavo-convex data
received in step S1301 as in. Next, in step S1403, the control unit
120 initializes the values of all pixels in N-value data out (since
the number of times of ink ejection is 0, 1, . . . , or 16, N=17)
indicating the number of times of ink ejection for each pixel.
Next, in steps S1404 to S1410, the concavo-convex data in is
quantized to the N-value data out through threshold processing.
FIGS. 15A to 15D show an example of a threshold matrix group used
in the threshold processing. In a case of performing conversion to
17-value data, 16 threshold matrices are required. In step S1405,
the control unit 120 reads the threshold matrices, allocates these
matrices in a tile-like pattern, and, in step S1407, performs
comparison of magnitude correlation between each of the threshold
values and a corresponding target pixel in the concavo-convex data
in. In FIG. 14, W expresses the number of columns in the matrix and
H expresses the number of rows in the matrix. Specifically, in step
S1407, the control unit 120 determines whether the value of the
target pixel in the concavo-convex data in is greater than the
threshold value of a coordinate position periodically corresponding
to the target pixel in a matrix [i] and is equal to or less than
the threshold value of a coordinate position periodically
corresponding to the target pixel in a matrix [i+1]. In a case
where the value of the target pixel in the concavo-convex data in
is greater than the threshold value of the coordinate position
periodically corresponding to the target pixel in the matrix [i]
and is equal to or less than the threshold value of the coordinate
position periodically corresponding to the target pixel in a matrix
[i+1], the processing proceeds to step S1408. Then, i is assigned
as the value of a pixel in the N-value data out which is at the
same coordinates as the target pixel. For example, the value of
each pixel in the N-value data out is determined in the following
way: in a case where the value of the target pixel is greater than
the corresponding threshold value in the matrix [1] and is equal to
or less than the corresponding threshold value in the matrix [2],
the number of times of ink ejection for this target pixel is set to
one. This processing is processing called multi-value dither
processing. Moreover, the method of conversion to N-value data may
be a multi-value error diffusion method which is a method generally
known as error diffusion method expanded for multi-value. In the
error diffusion method, quantization is performed based on
quantized error occurring in pixels near the target pixel. As
described above, the concavo-convex data is quantized in such a way
that the average value of the height of the concavo-convex data and
the average value of the height indicated by the N-value data are
substantially equal in any local region including the target
pixel.
[0101] The threshold matrices used in the aforementioned
multi-value dither processing can be generated in the following
method for example. FIG. 16 shows a threshold matrix which is a
base of the threshold matrices in FIGS. 15A to 15D. In this case, a
matrix called Bayer dither matrix is generally used. Multiple
threshold matrices for the multi-value dither processing are
calculated by using a formula of matrix [i] (x,
y)=(i-1).times.16+Bayer(x, y), where the threshold value of each of
pixels in the Bayer dither matrix is Bayer(x, y). In this formula,
i expresses the number of the threshold matrix. However, the
aforementioned matrix generation method is merely an example, and
matrices generated in any publicly-known technique can be used.
[0102] FIGS. 17A to 17D are views showing examples of
concavo-convex data and N-value data generated by performing the
aforementioned N-value processing of step S1302 on the
concavo-convex data. FIG. 17A shows concavo-convex data inputted in
a case where a layer with a thickness of 20 .mu.m is to be formed,
and FIG. 17B shows the result of N-value conversion on the
concavo-convex data of FIG. 17A. In this case, since a layer formed
at the ink amount of 100% has a thickness of 20 .mu.m, the number
of times of ink ejection is one for all pixels as shown in FIG.
17B. Meanwhile, FIG. 17C shows concavo-convex data inputted in a
case where a layer with a thickness of 30 .mu.m is to be formed.
FIG. 17D shows the result of N-value conversion on the
concavo-convex data of FIG. 17C. Since the thickness of 30 .mu.m is
a thickness between the thickness of one layer and the thickness of
two layers, pixels in which the number of times of ejection is one
and pixels in which the number of times of ejection is two exist at
a ratio of 50:50 as shown in FIG. 17D.
[0103] Next, in step S1303, the control unit 120 divides the
N-value data obtained in step S1302 to generate binary division
data indicating on and off of the ink for each pixel in each pass
in multi-pass printing (pass separation processing). FIG. 18 is a
flowchart showing details of step S1303. First in step S1802, the
control unit 120 reads the N-value data generated in step S1302 as
in2. Next, in step S1803, the control unit 120 initializes all of
pixels in binary data out2 [1] to binary data out2 [N-1]. Binary
data out2 [i] is data indicating on-off control of the ink in the
i-th pass. Specifically, in a pixel in which the binary data out2
[i] is 1, the ink is ejected in the i-th pass. Meanwhile, in a
pixel in which the binary data out2 [i] is 0, no ink is ejected in
the i-th pass. Then, in steps S1804 to S1810, the control unit 120
allocates the N-value data in2 to a pattern indicating on and off
of the ink for each pixel in each pass. Here, i in step S1804
indicates the number of pass, and the numbers are assigned
sequentially to a first pass, a second pass, and so on from a
smaller number. Specifically, a pattern of i=1 is formed in the
lowermost layer of the concavo-convex and a pattern of i=N-1 is
formed on the uppermost layer. In step S1806, the control unit 120
determines whether the value of the target pixel in the N-value
data in2 is 1 or more. In a case where the value is 1 or more, the
control unit 120 assigns 1 as the value of a pixel corresponding to
the target pixel in the binary data out2 [i] in step S1807. Then,
in step S1808, the control unit 120 sets a value obtained by
subtracting 1 from the value of the target pixel in the N-value
data in2 as the value of the target value. In other words, the
control unit 120 decrements the value of the target pixel. This
processing is repeated with all of the pixels sequentially set as
the target pixel. After the processing is performed with all of the
pixels set as the target pixels, i is updated and the same
processing is repeated again. As described above, in steps S1806 to
S1808, the processing of sequentially allocating values to the
binary data out2 is repeated in a case where data of 1 or greater
exists in the inputted N-value data in2. FIGS. 19A to 19C show
binary division data generated from the N-value data of FIG. 17D.
In this example, 1 indicates on of the ink and 0 indicates off of
the ink. FIG. 19A is a pattern of i=1 (first pass), FIG. 19B is a
pattern of i=2 (second pass), and FIG. 19C is a pattern of i=3 and
the following passes. In this example, a layer corresponding one
layer is formed in the first pass and a layer corresponding to 0.5
layers is formed in the second pass, and the total thickness is 30
.mu.m.
[0104] Lastly, in step S1304, the concavo-convex forming apparatus
forms concavo-convex based on the determined binary division data.
Moreover, the concavo-convex forming apparatus prints an image on
the formed concavo-convex as needed.
[0105] As described above, controlling the height through the area
coverage modulation enables formation of concavo-convex with a
height which cannot be formed only by stacking uniform layers of
the ink amount of 100%.
Embodiment 5
[0106] In Embodiment 4, description is given of the example in
which a layer having a thickness less than one layer can be formed
by controlling the height through the area coverage modulation. In
the case of forming a layer having a thickness less than one layer,
fine concavo-convex is sometimes formed. For example, even in a
case where a flat surface shape is desired to be formed by
performing the area coverage modulation as in FIG. 19B, the ink is
not ejected in all of the pixels but is sparsely ejected.
Accordingly, fine concavo-convex is sometimes formed. The
concavo-convex is more visible particularly in a case where the
number of times of ink ejection is small and the ink is ejected
more sparsely. In the embodiment, description is given of a method
of reducing fine concavo-convex and forming a smooth layer. There
are several methods of reducing fine concavo-convex. Description is
given below of portions of processing which are changed from those
of Embodiment 1 and Embodiment 4.
[0107] First change is made in the N-value processing described in
step 1302 of Embodiment 4. In the embodiment, a matrix called
dispersion matrix is used as the matrix used in the multi-value
dither processing. By using the dispersion matrix, pixels in which
the ink is ejected are dispersed evenly and difference in the
degree of sparseness of the ink is less likely to occur in a local
region. A blue noise mask method and the like are known as a method
of generating the dispersion matrix. Moreover, this objective can
be achieved also by using multi-level error dispersion processing
for the N-value conversion. Meanwhile, in Embodiment 1, it is only
necessary to change the binarization processing of step S606 to
processing in which binarization is performed by a dither method or
an error dispersion method which similarly uses the dispersion
matrix.
[0108] The second change is changing of the stacking order of
layers. In step S1804 of Embodiment 4, the order of i indicating
the stacking order of layers in loop 1 is changed to the descending
order. In a layer of FIG. 19B, pixels in which the ink is ejected
and pixels in which no ink is ejected mixedly exist and fine
concavo-convex is likely to be formed. If this layer is formed as a
surface layer, the fine concavo-convex is likely to be perceived.
To solve this problem, the fine concavo-convex is reduced in the
following way. The formation order of the layers is determined such
that the layer of FIG. 19B is not formed as the outermost surface,
and a relatively-smooth layer in which the ink is ejected in all of
pixels is formed on a layer having fine concavo-convex to cover
this layer. In the processing of Embodiment 1, in step S605, the
slice data stacking order is determined such that the slice data
corresponding to the ink amount of 100% is set as the slice data
for the outermost surface.
[0109] The third change is controlling the ratio of division of ink
ejection in the pass division step of step S1303 in Embodiment 4.
Specifically, in a case where a shape having a height corresponding
to, for example, an ink amount of 125% is desired to be formed, the
total ink amount of 125% is not divided into 100% and 25% which are
ink amounts to be ejected in the respective passes. Instead, the
pass division is performed such that there is no pass in which the
ink amount is small (in this example, 25%) and the total ink amount
of 125% is divided into, for example, 50% and 75%. Such division is
performed because fine concavo-convex is more visible in a case
where the number of times of ink ejection is small. On the other
hand, in a case where the number of times of ink ejection is great,
ink droplets are connected to each other to cover the entire
surface and form a smooth surface. Examples of pass division in a
case where the division is performed in the ratios described above
are shown in FIGS. 20A to 20E. FIG. 20A shows N-value data which is
original data to be divided (indicates an ink amount of 125%).
Pieces of binary division data obtained in a case where the ink
amount is divided into 100% and 25% as a division example 1 are
shown in FIGS. 20A and 20C. Pieces of binary data obtained in a
case where the ink amount is divided into 50% and 75% as a division
example 2 are shown in FIGS. 20D and 20E. In the division example
2, there is no pattern in which the number of times of ink ejection
is small as in FIG. 20C. In the processing of Embodiment 1, it is
only necessary to distribute the concavo-convex data in the slice
processing step of step S602 such that each layer has a height
corresponding to an ink amount of a certain percentage. In this
case, in a case where the patterns of pieces of binary division
data for respective passes are similar to each other, the degree of
fine concavo-convex increases depending on the way the patterns are
overlapped. Accordingly, it is desirable to change the matrices of
dither processing for the respective layers to ones different from
each other.
[0110] An example of a method of the division is given. For
example, in a case where a height corresponding to, for example, an
ink amount of 210% is desired to be formed, 210 is divided by three
to be substantially-evenly divided into 70, 70, and 70. This is
calculated by dividing the target ink amount by the minimum number
of passes required to obtain the height corresponding to the target
ink amount (for example, in a case where the ink amount is 250, the
ink amount is divided by three; in a case where the ink amount is
360, the ink amount is divided by four). In other words, the
calculation is performed by dividing X by a number obtained from
int (X/100)+1, where X is the percentage of the ink amount (decimal
part of int is dropped). Such calculation enables division to be
performed in such a way that a pass in which the number of times of
ink ejection is small is less likely to occur. Note that expression
"substantially-evenly" is used in the meaning of allowing a certain
width of variation among the ink amounts obtained by division. For
example, in the aforementioned case where the height corresponding
to the ink amount of 210% is to be formed, the ink amount can be
divided into 70%, 70%, and 70%, as a matter of course, and can be
also divided into, for example, 60%, 70%, and 80%. Specifically, as
long as the ink amounts obtained by the division are within a range
obtainable by: converting a piece of binary division data which is
originally 100% into data which is not 100%; and adding the ink
amount subtracted from this data to another piece of binary
division data which is originally not 100%, the division is within
the scope of "substantially-evenly." The idea described above can
be applied to a method including a step of generating slice data as
in Embodiment 1. In this case, in step S602, the obtained
concavo-convex data is not divided at the contour lines provided at
intervals corresponding to the ink amount of 100%. Instead, as in
the idea described above, for example, the ink amount of 210% is
divided into 70%, 70%, and 70% or 60%, 70%, and 80%.
[0111] As described above, it is possible to reduce fine
concavo-convex and form a smooth layer in a case where a layer
having a thickness less than one layer is formed by area coverage
modulation.
Other Embodiments
[0112] In the embodiments described above, description is given of
the examples in which the data indicating on and off of the ink is
generated from the concavo-convex data indicating the height of the
concavo-convex in each pixel. However, the following mode can be
employed. A data generation apparatus such as an external computer
generates the data indicating on and off of the ink from the
concavo-convex data and transmits the generated data to the
concavo-convex forming apparatus. Such a data generation apparatus
may function also as the control unit of the concavo-convex forming
apparatus, as a matter of course.
[0113] Embodiment(s) of the present invention can also be realized
by a computer of a system or apparatus that reads out and executes
computer executable instructions (e.g., one or more programs)
recorded on a storage medium (which may also be referred to more
fully as a `non-transitory computer-readable storage medium`) to
perform the functions of one or more of the above-described
embodiment(s) and/or that includes one or more circuits (e.g.,
application specific integrated circuit (ASIC)) for performing the
functions of one or more of the above-described embodiment(s), and
by a method performed by the computer of the system or apparatus
by, for example, reading out and executing the computer executable
instructions from the storage medium to perform the functions of
one or more of the above-described embodiment(s) and/or controlling
the one or more circuits to perform the functions of one or more of
the above-described embodiment(s). The computer may comprise one or
more processors (e.g., central processing unit (CPU), micro
processing unit (MPU)) and may include a network of separate
computers or separate processors to read out and execute the
computer executable instructions. The computer executable
instructions may be provided to the computer, for example, from a
network or the storage medium. The storage medium may include, for
example, one or more of a hard disk, a random-access memory (RAM),
a read only memory (ROM), a storage of distributed computing
systems, an optical disk (such as a compact disc (CD), digital
versatile disc (DVD), or Blu-ray Disc (BD).TM.), a flash memory
device, a memory card, and the like.
[0114] In the present invention, it is possible to form an uneven
shape having excellent characteristics by taking in consideration
of reproduction characteristics of sharpness and smoothness in
concavo-convex formation processing.
[0115] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0116] This application claims the benefit of Japanese Patent
Application No. 2014-137905, filed Jul. 3, 2014, which is hereby
incorporated by reference wherein in its entirety.
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